1. Field of the Invention
The present invention relates to vehicle motion control systems, and more particularly to a vehicle motion control system for accelerating or decelerating a vehicle so that the vehicle has an adequate motion state.
2. Background Art
Conventionally, a system has been known which decelerates a vehicle when lateral acceleration generated on the vehicle becomes larger than a set value based on curve information of a navigation system or a lateral acceleration at the time of turning (see, for example, JP Patent Publication (Kokai) No. 2009-51487).
In such a system, a target vehicle speed at the time of driving a curve is set from a preset lateral acceleration set value and a curve curvature ahead of an own vehicle so that the magnitude of a lateral acceleration generated at the time of passing the curve is not more than the set value. A necessary deceleration is produced based on both of the target vehicle speed and an actual vehicle speed. Producing the deceleration in such a way is effective for suppressing departure from a road when the vehicle enters into a curve at a speed exceeding a limit speed at which the vehicle can turn the curve.
However, when deceleration control before a curve is performed by setting as the set lateral acceleration not a turnable lateral acceleration limit but a lateral acceleration that a driver can presumably tolerate at normal turning, it is not necessarily assured that the performed deceleration sufficiently corresponds to a sensory deceleration of the driver. This may partly be attributed to the fact that in the aforementioned method for producing the deceleration based on the target vehicle speed, the total deceleration before entering into the curve (deceleration integral value) can be defined but a temporal change of the deceleration cannot be defined.
If deceleration control is carried out so that the deceleration before curves is constant, the performed deceleration may not sufficiently correspond to a sensory deceleration of the driver depending on curves and vehicle speeds. Setting a temporal change of the deceleration for every curve requires a large number of adaptation steps and a vast quantity of data.
As a method for defining the temporal change of the acceleration and deceleration which sufficiently corresponds to a sensory deceleration of the driver, a method for producing acceleration and deceleration based on a lateral jerk generated by operation of the driver has been proposed (see, for example, JP Patent Publication (Kokai) No. 2008-285066 and Transactions of Society of Automotive Engineers of Japan, Vol. 39, No. 3, 2008). This method makes it possible to carry out acceleration and deceleration in the same way as by skilled drivers without setting the temporal change of the deceleration for every curve.